b. Ionosphere helps us in communication through mobile phones.
Answers
Answer:
In particular the ionosphere is widely known for affecting signals on the short wave radio bands where it "reflects" signals enabling these radio communications signals to be heard over vast distances.
Answer:
The ionosphere does not provide anything that is required for radio communications but it can enhance the ability of some wavelengths to propogate greater terrestrial distances.
Especially at medium wave (300–3,000 kc) and short wave (3,000–30,000 kc) frequencies, the charged ionosphere will act as a reflector, bouncing signals back down to the Earth. Depending on a number of variables such as time of day, season and solar activity, this may allow for reception hundreds or thousands of miles from the transmitter.
Although somewhat variable and at times unpredictable, it is possible to make generalized predictions as to how the ionosphere will affect certain radio emissions at given times. International shortwave stations use this to their advantage; by selecting the right frequency band at a certain time of day and directionalizing their transmissions, these stations can reliably provide service to desired areas of the world. Many of these destinations are in either underserved or underdeveloped countries or nations where such transmissions would be prohibited.
Using this technology as a hobby is one of the major reasons the amateur radio service is popular. Given the right conditions, you can communicate with someone almost anywhere on the planet with only a 100-watt transmitter.